L3 C3 P3 : Tricarbontriphosphide Tricyclic Radicals and Cations Stabilized by Cyclic (alkyl)(amino)carbenes.

Alkynes usually oligomerize to give rings with a conjugated π-electron system. In contrast, phosphaalkynes, R-C≡P, frequently give compounds with polycyclic structures, which are thermodynamically more stable than the corresponding π-conjugated isomers. The syntheses of the first C3 P3 tricyclic compounds are reported with either radical or cationic ground states stabilized by cyclic (alkyl)(amino)carbenes (CAACs). These compounds may be considered as examples of tricarbontriphosphide coordinated by carbenes and are likely formed via trimerization of the corresponding mono-radicals CAAC-CP. . The mechanism for the formation of these tricarbontriphosphide radicals has been rationalized by a combination of experiments and DFT calculations.